An installation for converting hydraulic energy into electrical energy includes at least a turbine, having a shaft connected at a first end to a runner, which is the rotating part of the turbine. The installation also includes a generator for connecting the turbine to the grid. The generator has a rotor that is connected at a second end of the shaft. The shaft is then subjected, at its first end, to a positive torque exerted by the runner and, at its second end, to a negative torque exerted by the generator. The turbine shaft is supported and guided in rotation by fluid bearings. An oil film is radially interposed between the shaft and a rigid body of the bearing.
The turbine shaft has an elongated shape. Its length may indeed exceed 20 meters. As a result, any defect in the machine leads to important shaft vibrations under the excitation formed by the torques applied at both ends of the shaft. Typical defects are shaft misalignments within the bearings, cracks, machine unbalance, shaft flexion, torsion.
It is then important to monitor the shaft vibrations so as to evaluate the operating status of the machine. For example, new machines vibrate less than older machines. A method consists in equipping fluid bearings with displacement probes so as to measure the radial clearance between the shaft and the bearing rigid body. This allows preventing the shaft from crushing the bearing oil film. Accelerometers (or velocity probes) can also be embedded on the shaft bearings so as to determine the efforts exerted by the shaft on the bearings along the three directions of a local space reference.